Spondylolysis (Pars Fracture of the Spine)

David Green, MD2006 Sports Medicine and Shoulder FellowHospital for Special Surgery

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Overview

Spondylolysis occurs when there is a crack in the bony posterior (rear) portion of the spinal column. The human spine is made up of 24 bones - called vertebrae - which are stacked on top of one another in the spinal column.

The spinal cord is protected by a ring of bone that makes up the middle and posterior portion of the spinal column. The area of injury in the spinal column is between the pedicle and lamina. (see figure 1)

This is usually caused from excessive or repeated strain to the area of the spinal column called the pars interarticularis, and it is sometimes referred to as a pars defect when fractured through this portion of the spinal column. (see figure 1)

Figure 1: Depiction of the Spinal Column and Location of a Pars Fracture

View from the side

View from the top

The lower portion of the spinal column is called the lumbar spine. Spondylolysis most commonly occurs in the lower back at lumbar vertebra number five (L5). In athletes, this type of injury can be seen when the back is bent backwards repeatedly, in activities such as gymnastics, karate, and football. Specifically, this is common in offensive and defensive linemen.

The vertebra initially responds to increased strain by gradually adding new bone cells around the injured area; however, an injury can occur too quickly for the vertebrae to be repaired, and this leads to a stress fracture. This type of fracture usually occurs in the pars and can lead to a persistent pars defect after the fracture has been completed.

The crack may affect only one side, but it is not uncommon to have fractures on both sides of the vertebra. When fractures occur on both sides, it is possible for one vertebra to translate or move forward or backward over the neighboring vertebra; this is called spondylolisthesis.

Symptoms

Those with a pars fracture may feel pain and stiffness in the lower back that is worsened with activity and improves with rest. Hyper-extension (abnormal stretching) of the lower back will usually aggravate the area as it overloads the pars fracture.

Occasionally, nerve symptoms can be present that may include a “pins and needles” sensation in a leg, with or without numbness or weakness in the leg.

Diagnosis

Evaluation for this condition would include a review of the patient’s medical history and a physical exam, followed by x-rays, which can detect pars defects.

A bone scan can be used for early detection of a stress fracture of the pars. This involves injecting chemical "tracers" into your blood stream. The tracers then show up on special spine x-rays. The tracers collect in areas of increased metabolism or cell activity in bone tissue, such as would be seen in areas of a stress fracture of the pars interarticularis.

A CT scan be used to evaluate a pars defect and to visualize healing bone, while an MRI may be useful to assess the surrounding tissue and condition of the disk.

Treatment

The treatment for a pars fracture is initially non-operative and includes rest and bracing. The fracture can be assessed with a series of x-rays every few months.

Bracing can last for 3-4 months while the fracture heals, and physical therapy can also be included to maintain and help strengthen the abdominal and back muscles with specific directed exercises.

If the athlete has persistent pain after non-operative treatment, surgery may be required. There are two operations that may be performed:

A laminectomy, which refers to a procedure in which the surgeon removes that portion of the vertebra that includes the pars interarticularis. This is used if there are nerve roots being affected that require decompression.

A posterior lumbar fusion, if a spinal segment has become loose or unstable. A spinal fusion allows two or more bones to grow together, or fuse, into one solid bone. This keeps the bones and joints from moving. Rehabilitation will start six weeks after surgery to allow the bone to heal (fuse). Therapy will usually last for 6-8 weeks, and a patient should expect full recovery to take up to six months.